The Role of Membrane-Associated E3 Ubiquitin Ligases in Cancer.

The cell membrane system comprises the plasma membrane, endoplasmic reticulum, Golgi apparatus, lysosome, mitochondria, and nuclear membrane, which are essential for maintaining normal physiological functions of cells. The proteins associated with these membrane-organelles are frequently modified to regulate their functions, the most common of which is ubiquitin modification. So far, many ubiquitin E3 ligases anchored in the membrane system have been identified as critical players facilitating intracellular biofunctions whose dysfunction is highly related to cancer. In this review, we summarized membrane-associated E3 ligases and revealed their relationship with cancer, which is of great significance for discovering novel drug targets of cancer and may open up new avenues for inducing ubiquitination-mediated degradation of cancer-associated membrane proteins via small chemicals such as PROTAC and molecular glue.

Noncovalent CDK12/13 dual inhibitors-based PROTACs degrade CDK12-Cyclin K complex and induce synthetic lethality with PARP inhibitor.

Cyclin-dependent kinase 12 (CDK12) plays a crucial role in DNA-damage response gene transcription and has recently been validated as a promising target in cancer therapy. However, existing CDK12 inhibitors potently inhibit its closest isoform CDK13, which could cause potential toxicity. Therefore, the development of CDK12 inhibitors with isoform-selectivity against CDK13 continues to be a challenge. By taking advantage of the emerging PROteolysis-TArgeting Chimeras (PROTACs) approach, we have synthesized a potent PROTAC degrader PP-C8 based on the noncovalent dual inhibitors of CDK12/13 and demonstrated its specificity for CDK12 over CDK13. Notably, PP-C8 induces profound degradation of cyclin K simultaneously and downregulates the mRNA level of DNA-damage response genes. Global proteomics profiling revealed PP-C8 is highly selective toward CDK12-cyclin K complex. Importantly, PP-C8 demonstrates profound synergistic antiproliferative effects with PARP inhibitor in triple-negative breast cancer (TNBC). The potent and selective CDK12 PROTAC degrader developed in this study could potentially be used to treat CDK12-dependent cancers as combination therapy.

Structure-based rational design enables efficient discovery of a new selective and potent AKT PROTAC degrader.

AKT and associated signaling pathways have been recognized as promising therapeutic targets for decades, and growing evidence indicates that inhibition or degradation of cellular AKT are viable strategies to treat cancer. Guided by an in silico modeling approach for rational linker design and based on our previous work in this field, we herein efficiently synthesized a small group of cereblon-recruiting AKT PROTAC molecules and identified a highly potent AKT degrader B4. Compared to the existing AKT degraders, B4 has a structurally unique AKT targeting warhead derived from the pyrazole-furan conjugated piperidine derivatives. It induces selective degradation of all three isoforms of AKT and exhibits efficacious anti-proliferation against several human hematological cancers. Notably, B4 demonstrates potent inhibition of AKT downstream signaling superior to its parental inhibitor. Together with its active analogs, B4 expands the arsenal of AKT chemical degraders as a valuable probe to uncover AKTs new functions and as a potential drug candidate to treat cancer.